Runner #2 (from the left):
Natural lean
Knee drive (hip flexion, pulling through)
Neutral ankle, foot dangles for midfoot strike

Runner #3:
Heel-to-butt action
Weight over strike foot

Each characteristic  is “running”; opens up the possibilities of speed/results.

Runners 1, 4, 5:
Weight back, behind strike foot
No heel to butt (leg lagging out the back)
No knee drive (leg scissoring out the front)
Toes pointed up (flexed ankle) leading to the dreaded heel strike

Each characteristic is “running with the brakes on”; opens up the possibilities of slow/imbalances/injury.

What to do?
Run unadulterated, free, and open…the way we did as kids…before all the nonsense “jogging” “running to stay fit” “training for a race.” Sure, you could read all about Pose, Chi, etc (which is highly recommended)…but that can even adulterate this simple concept…run natural, run fearless, run fast.

Overheard at CF:
“It’s just like Bear Crawl Drill only with more Bends & Thrusts.” (Nice, very nice!)